The traditional satellite television receiving system refers to a satellite earth receiving station comprised of a parabolic antenna, a feed, a low-noise block downconverter, also called a low-noise block (LNB), and a satellite receiver. The parabolic antenna is intended to reflect satellite signals to the feed at the focal point of the antenna and to the LNB. The feed is a horn (also called a corrugated horn) located at the focal point of the parabolic antenna for receiving satellite signals. The feed has mainly two functions: one is to collect the electromagnetic waves received by the antenna, convert them into signal voltages, and then transmit them to the LNB; the other is to convert the polarization of the received electromagnetic waves. An LNB is used to downconvert satellite signals sent by the feed, amplify them, and then transmit them to a satellite receiver. Generally, LNBs can be divided into C-band frequency LNB (3.7 GHz-4.2 GHz, 18-21 V) and Ku-band frequency LNB (10.7 GHz-12.75 GHz, 12-14 V). An LNB amplifies high frequency satellite signals to hundreds of thousands of times larger, and then convert the amplified signals through a local oscillator circuit to an intermediate frequency (950 MHz-2050 MHz) so as to facilitate signal transmission through coaxial cables and demodulation by the satellite receiver. The satellite receiver demodulates the satellite signals passed by the LNB to satellite television images or audio and digital signals.
When receiving signals, a parabolic antenna reflects and converges the parallel electromagnetic waves to the feed. Normally, the feed of a parabolic antenna is a horn antenna.
However, manufacturing of parabolic antennas is complicated and costly because of great difficulties in and high precision requirements for processing the curve of a parabolic reflector.